Boosted and Ballistic: A 350-pound nitrous-fuelled W650

It might have immaculate retro style, but you wouldn’t pick the Kawasaki W650 for its performance. With 50 horses on tap it’s a fun enough runabout—and you could squeeze out a little more out with exhaust and intake work. But it’s no wheelie machine.

No one bothered telling Tom Thöring of Schlachtwerk though. Every time he builds another W650, he finds new and creative ways to extract more goodness from the long-stroke parallel twin. We’ve seen W650s with 58 and 70 hp roll off his bench—but this time he’s pulled out literally every stop.

This 1999-model W650 (now a ‘W854’) delivers a healthy 82 hp to the back wheel, and excludes the extra kick from the nitrous system. Yes—this W comes with a liquid boost.

Tommy built the bike for a friend in nearby Frankfurt, who regularly accompanies him to the Sultans of Sprint races. “He loves the sprint series,” says Tommy. “At the race he helps to push start my bike, and he gives me last minute instructions like a coach.”

Tommy’s friend—nicknamed Macaco—decided he wanted a race bike of his own for next year’s Sultans of Sprint series. So he commissioned Tommy to build him a light and sporty W650 racer that’d still be practical for sunny weekend rides.

Tommy obliged, and straight away bored out the Kawa motor to 854 cc. It’s now sporting ported heads, race camshafts and a reinforced clutch. The stock carbs are still in play, but they’ve been rejetted and mated to K&N filters. (A set of Mikuni flatslide carbs is on the to-do list). And the exhaust is a completely custom stainless steel affair, right up to the under-seat muffler.

Macaco’s W854 is also fitted with a very handy quickshifter—but fitting it was no cakewalk. “I had to change the whole footrest system,” says Tommy, “because for the sensor I needed a gearstick, or rod, to integrate it.” He’s used LSL rear sets, which also had to be modded to accommodate the kickstarter.

Then there’s the NOS. Tommy used a wet system with a programmable controller, from Nitrous Express. Installing the ignition kill module was easy, but squeezing the nozzles in between the carbs and engine was far trickier.

He breaks down how the system works: “After arming the system, the start signal for the extra power is a wide open throttle (WOT) sensor. The WOT starts the extra power, and the controller increases the additional power smoothly—so it’s not like a bull kicking your ass.”

“With the selected jets I can add 50 more horsepower to the bike, but the system is able to give much more. The setup is working really well: since Macaco lost his Nitrous virginity, he can’t stop laughing on the bike.”

You’d think all that boost would call for some serious frame mods, but Tommy disagrees. He’s made hardly any changes to the frame, save for revising the passenger peg mounts. Instead, he turned his attention to the W’s real weak spots: suspension and brakes.

The spindly stock front end has given way to a set of triples and upside-down forks from a 2005 Yamaha R1. Out back is a custom-made aluminum swingarm, 90 mm longer than stock and with 80 mm of adjustment to switch between race and street geometry. Holding up the rear is a new pair of shocks from YSS.

As for the brakes, Tommy’s installed a Suzuki GSX-R1000 caliper, 320mm Pro Brake disc and Magura HC1 master cylinder up front. The rear’s been converted from a drum to a disc, with a two-piston Brembo caliper doing duty.

The wheels are new too. Gone is the standard 19F/18R spoked combination, replaced by a pair of forged alloy hoops that Tommy commissioned specifically for this bike. The front measures in at 2.5×18” with a 110/80 Conti Road Attack, and the rear is a 4.0×18” with a 150/65 Conti Classic Race.

Up top is a custom-made, 9l aluminum fuel tank, kitted with a Monza gas cap. The paint color is BMW ‘Le Mans’ blue, and the Korean writing on the tank reads ‘Macaco’ (he has Korean roots). “The paint job is done by a nice guy called Paolo,” says Tommy. “Every time I take bike parts over for painting, he rolls his eyes, but his work is really good.”

The seat’s custom too, made to cover the full length of the frame and carry a passenger if needed. Finishing kit includes R1 clip-ons, a Motogadget speedo, new head and taillights on custom brackets, and tiny Kellerman turn signals.

Tommy’s changes have resulted in a significant overall weight saving. The new wheels are 24 pounds (11 kg) lighter than stock, the new exhaust system only weighs 7.7 pounds (3.5 kg) and the swingarm is significantly more svelte. Tommy’s also removed the Kawasaki’s heavy electric starter, and fitted the smallest battery he could—a small 1.1 Ah unit, hiding in a tray under the seat.

The bike now weighs in at 356 pounds (161.5 kg), and that’s with all liquids onboard. With 82 horsepower at the ready and proper brakes and suspension to back it up, it should have no problem tearing up backroads on the weekends.

And when Macaco’s ready to hit the track, he only needs to let out the extra 80mm of wheelbase, fill the NOS bottle…and hold on tight.